1. Field of the Invention
The invention relates to an image-capturing apparatus, and more particularly, to an image-capturing apparatus capable of effectively removing dust by vibrating a vibration plate in a plurality of vibration modes.
2. Description of the Related Art
Recently, pixel pitch has been decreasing as the number of pixels implemented by imaging devices has increased. Dust stuck on an optical device near an image surface of an imaging device may be included in a captured image, and thus, may deteriorate image quality.
In order to solve this problem, U.S. Patent Publication No. 2004/0169761 describes a feature in which, with respect to one driving frequency input to an oscillator (a piezoelectric element), only one resonance mode that is effective for dust removal occurs in an optical device unit including the oscillator. When two or more driving frequencies are sequentially input to the oscillator to form complementary vibrations, two or more resonance modes that are effective for dust removal sequentially occur.
However, as described in U.S. Patent Publication No. 2004/0169761, when two or more driving signals of different frequencies are sequentially input to the oscillator a vibration node exists for each frequency, although positions of the vibration nodes vary according to frequencies of the driving signals. Because the vibration amplitude is 0 at the vibration nodes, although the frequencies vary, the efficiency of dust removal deteriorates at the position of the vibration node for each frequency.
Also, according to U.S. Patent Publication No. 2004/0169761, it is necessary to input two or more driving signals of different frequencies to the oscillator. However, this increases manufacturing costs due to a more complicated driving circuit.
Japanese Patent Publication No. 2010-119049 describes simultaneous input of two driving signals of different frequencies to respective vibration members, creating two different resonance modes that are simultaneously effective for dust removal.
However, according to Japanese Patent Publication No. 2010-119049, because it is necessary to separately form the two vibration members that operate at different frequencies, device configuration becomes more complicated, the number of parts increases, and the number of manufacturing processes increases resulting in an increase manufacturing costs. Also, due to the use of two vibration members, it is necessary to arrange a relatively large space in an apparatus, which may make it difficult to reduce the size of the apparatus.